Ses Dosyalarının ENF Tabanlı Adli Analizine Kısa Zamanlı Fourier Dönüşümü Parametre Seçimlerinin Etkisi

Yıl 2023, , 79 - 87, 30.04.2023

Ali Berk Yalınkılıç , Saffet Vatansever

https://doi.org/10.46387/bjesr.1246180

Öz

Hızla gelişmekte olan bilgisayar teknolojisi sayesinde çeşitli tekniklerle dijital
ses, görüntü ve video dosyaları üzerinde modifikasyonlar yapılabilmektedir.
Bu modifikasyonlar doğrudan dosya içeriğinde olabileceği gibi bazen de meta
data üzerinde olabilmektedir. Bu bağlamda dijital medyaların adli analizi
büyük önem arz etmektedir. Elektrik şebeke frekansı (ENF) tabanlı adli analiz
yaklaşımı dosya bütünlük kontrolünde ve dosyaların kayıt zamanı tespitinde
kullanılabilen önemli bir araçtır. ENF sinyali kestiriminde en çok tercih edilen
yöntemlerden biri, kısa zamanlı Fourier dönüşümü (Short-Time Fourier
Transform - STFT) temelli yaklaşımdır. STFT yönteminde, pencere boyutu ve
kaydırma miktarı parametrelerinin seçimi büyük öneme sahip olup, kestirimi
yapılan ENF sinyali doğruluğunu, dolayısıyla da ENF tabanlı adli analiz
uygulamalarının performansını doğrudan etkileyebilmektedir. Bu çalışmada,
STFT parametreleri seçiminin, ENF tabanlı dosya kayıt zamanı doğrulamada
performansa ne derece etki ettiği araştırılmıştır. Farklı uzunluktaki ses
dosyaları, çeşitli STFT pencere boyutu ve STFT kaydırma miktarlarına göre
ayrı ayrı test edilerek karşılaştırmalı bir analiz yapılmıştır.

Anahtar Kelimeler

ENF, Elektrik Şebeke Frekansı, Ses ve Videoların Adli Analizi, Kayıt Zamanı, Zaman Damgası

Destekleyen Kurum

Bursa Teknik Üniversitesi

Proje Numarası

211N022

Teşekkür

Bu çalışma Bursa Teknik Üniversitesi Bilimsel Araştırma Projeleri birimi tarafından 211N022 numaralı proje kapsamında desteklenmiştir.

The Effect of Short-Time Fourier Transform Parameters Choice on ENF-based Forensic Analysis of Audio

Öz

Due to the rapidly developing computer technology, digital audio, image, and
video can be modified with various techniques. These modifications may be
on the media content or the metadata. In this context, forensic analysis of
digital media is of great importance. Electrical network frequency (ENF) based
forensic analysis is a significant tool that can be used for checking file integrity
and detecting time-of-recording. One of the most preferred methods for ENF
signal estimation is the Short-Time Fourier Transform (STFT) based
approach. The choice of STFT window size and STFT hop size can directly
affect the accuracy of ENF signal to be estimated from media, and hence the
performance of the ENF-related forensic applications. This work investigates
how the STFT parameters choice affects the performance in time-of-recording
verification. A comparative analysis is made for various STFT window sizes
and STFT hope sizes by experimenting with different audio lengths.

Anahtar Kelimeler

ENF, Electric Network Frequency, Audio and Video Forensics, Time-of-Recording, Time-Stamping

Proje Numarası

211N022

Kaynakça

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